<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <script>
    let s = Symbol();
    console.log(typeof(s)) // symbol

    const obj = {
      toString() {
        return 'abc';
      }
    }
    let s1 = Symbol(obj)
    console.log(s1) // Symbol(abc)

    let s2 = Symbol('boo')
    console.log(s2.description) // boo

    let s3 = Symbol()
    const obj2 = {}
    obj2[s3] = 'hello'
    obj2.name = 'tom'
    console.log(obj2) 
    // {
    //   name: "tom",
    //   Symbol(): "hello"
    // }
  </script>
</body>
</html>